Children Sing Science!
What's better than children singing? Children singing about science. And to take it once step better, give all the little kiddies British accents.
Apparently these videos have been around for quite some time, but I somehow missed them. Thus I'm guessing that some of you may have missed them as well.
The following are a couple of songs from David Haines Lifetime: a Science Oratoria. You can find a much larger list of songs here, as well as details on the project.
Beware: after listening this you will have "Kingdom...phylum...class and or-r-r-rder" stuck in your head all day long.
Taxonomy
Mr. Darwin, Mr. Wallace, Mr. Matthew
Adaptation of the Week – the Insect Dorsal Ocelli
Dog Day Cicada (wikipedia commons)
There's one particular event of every summer in the South that I always await with great anticipation: the emergence of the millions of annual Dog Day cicadas (Tibicen canicularis).
It's not just the event itself that I love. The cicadas are certainly wonders in themselves; but for me, they are more than just insects of the order Homoptera - they are the standard-bearers of my favorite time of year: the "dog days" of summer. It's the time of year when the sun shines the brightest, heat covers the land as lazy dogs curl in cool digs in the shade, and Sirius - the Dog Star and the brightest in the sky - makes its appearance above the Southern horizon.
Spring is nice. Fall is fairly beautiful. Winter could be thrown to the dogs and I wouldn't bat an eye. But Summer? Ahh, summer is the incubator of my soul. When I'm in it, the warmth makes my happiness grow as ideas sprout from the imaginal discs of my imagination.
It is in no small part the fact that cicadas choose late summer to burst newly reformed into the world, leaving their former larval stages behind, that they receive my respect. I like their style.
But they deserve my awe for many other reasons beyond our shared love of summer. Many of us are well aware of the cicadas' prolonged existence as grubs feeding amongst the roots of trees for years, the exact time dependent on the particular species. Many species have synchronized both their development and life-cycles to such a degree that they burst forth from the ground all at once after 13 or 17 years of sucking sap as larvae. They enjoy an incredibly short adulthood, frantically mating for a few weeks, followed by death en masse (much like the death orgies of the market squid).
The advanced life-cycle adaptations of the cicadas and the timing thereof are deserving of their own tribute. However, the focus of this article lies elsewhere in our cicadan wonders. For the cicada contains an organ prevalent among many orders of insects that many of you have likely never even heard of: the "dorsal ocelli".
"There are no more other worlds to conquer!" - Alexander the Cicada
"Did I play my role well? If so, then applause, because the comedy is finished!" - Cicadan Emperor Augustus
Dorsal Ocelli
I took the images above last summer after the poor (or perhaps ecstatically happy) little cicada had already performed its life duties. Shortly after emerging and mating, cicadas slowly become lethargic, then immobile, and finally they simply die. This individual had reached the immobile stage. It was still alive when these pictures were taken, but days later it had died - remaining in the exact same location and position you see it in now.
Now, look more closely. You may notice its head is bejeweled with three orange organs. These are its dorsal ocelli (singular: ocellus).
"It is during our darkest moments that we must focus to see the light." - Cicada Benson
The ocellus is a strange and still quite mysterious organ. It is present throughout the insect world, but only erratically. Despite their ongoing mystery, the organs have been studied fairly extensively since the 1920s and 30s. The following distribution of ocelli among the insects (for you entomologists) is from The Function of the Insect Ocellus1, by D. A. Parry in 1947:
ORTHOPTERA : always present in Acriidae and Gryllidae; sometimes present in Blattidae, Mantidae, Tettigoniidae; not present in Grylloblattidae. DERMAPTERA : absent. PLECOPTERA : two or three present. ISOPTERA: present. EMBIOPTERA: absent. PSOCOPTERA: sometimes present. ANOPLURA: absent. EPHEMEROPTERA: present. ODONATA: usually present. THYSANOPTERA: present. HEMIPTERA: great variation. Some families separated on the presence or absence of ocelli. Several families in which some genera possess ocelli and some do not. NEUROPTERA: conspicuous in some families, absent in others. MECOPTERA: some genera with ocelli, others without. TRICHOPTERA: some families with ocelli, others without. One family including six genera with ocelli and two without. LEPIDOPTERA: sometimes present. COLEOPTERA : absent except in a few species not all in the same family. STREPSIPTERA : absent. HYMENOPTERA: usually present, but sometimes absent in the Vespoidea. DIPTERA: sometimes present. APHANIPTERA: uncertain.
Many species it seems have found great use in the ocellus, as evidenced by its retention throughout much of the Insecta class, while others have completely disposed of it.
But what is it?
“If the sight of the blue skies fills you with joy, if a blade of grass springing up in the fields has power to move you, if the simple things in nature have a message you understand, Rejoice, for your soul is alive.” - Eleanora Cicada
Essentially, the dorsal ocellus is an eye. But dorsal ocelli are not like the large compound eyes always present nearby. Nor are they like our own.
Early studies measuring the focal depth of various ocelli lenses all came to the conclusion that ocelli cannot focus forms on their simple retinas. It has since been shown that this is mostly true, except with some dragonflies which apparently may be able to form images with their ocelli.
What dorsal ocelli can do quite well is sense light. In fact they are much more sensitive to light intensity than the main compound eyes.
Studies in the 40s showed that ocelli nerve impulses were inhibited by light. When the ocellus was occluded, signals would then propogate down the large nerves to ganglia. Essentially, if a shadow passed over the ocellus, signals fired. And because the nerves are very large in diameter (often the largest nerve fibers), they are very fast.
It was additionally shown that light perception in the ocelli alone could not lead to reflexive movement. Thus it was suggested, and some still hold, that light perception (or shadow perception) acts to set the excitatory potential of the nervous system. Thus, if a shadow passes overhead, the nervous system would be primed to react to visual stimuli from the compound eyes.
Advances in Insect Physiology
More recent studies have shown that ocelli are intricately involved in orientiation to light (including UV), particularly to the horizon, and so are integral parts of the flight stabilization machinery, which makes sense when considering that most flying insects have ocelli.
Again, research in dragonflies indicate that the ocelli can form images with very wide fields, and can sense motion. There are other indications that ocelli may play a role in circadian entraining.
To my knowledge, no physiological research has been conducted on the cicada ocelli. Regardless, it appears that whatever the function of the ocellus, it is intricately and physically intertwined with the circuitry of vision from the compound eyes.
The ocellus represents just one more example - among myriads - of a sense that we as humans can hardly fathom. It is hard enough to imagine perceiving the world through thousands of individual ommatidia (the many eyes within a single insect compound eye). Add to that a complex system of light perception wired to the eye circuitry to aid in orientation, flight stability, or to prime the brain for visual stimuli. Such perception is impossible to even imagine.
It's clear from my limited research that science has yet to fully explain the purpose of these beautiful adaptations, despite the prevalence of their existence. It just goes to show that we have not come close to deciphering all the mysteries of life - even mysteries that have stared us in the face for a century.
So this summer, as the cicadas raise their eyes and dorsal ocelli to the summer sun for the first and last time, take a second to give them a closer look. You may just find yourself in awe of these photosensitive jewels.
References
- Parry D.A. (1947) The Function of the Insect Ocellus. Journal of Experimental Biology. Vol. 24. Nos. 3 & 4. pp. 211-219 (pdf)
- Beament J.W. L. (1966) Treherne J.E. Advances in Insect Physiology. Academic Press. (book)
- Berry R.P., Stange G., Warrant E.J. Form vision in the insect dorsal ocelli: An anatomical and optical analysis of the dragonfly median ocellus. Vision Research. Volume 47, Issue 10, May 2007, pp. 1394-1409.
- Simple eyes in Arthropods. Wikipedia.org
Previous Adaptations of the Week:
What would YOU like to know about sharks?
Why do sharks matter?
One of my science blogger buddies, WhySharksMatter over at Southern Fried Science, has received the opportunity to interview an influential shark researcher, Dr. Dan Abel. He is asking for anyone and everyone to pose a question you would like asked of Dr. Abel. Perhaps you want to know something about sharks or maybe something about what it's like to study sharks or why he chose to study them. There are any number of fascinating things to be asked. I asked an interesting one myself (at least I think it's interesting).
So if you have any shark-related questions you'd like answered by an actual shark expert, head over to this post right now and leave your question in the comments section.
Self-Recognition in Apes
Here is an awesome NGC video I saw a while back. I dug it up because it goes along nicely with our ongoing conversation on Medical Research in Animal Models, including discussions of self-awareness in animals.
Be sure to check out the sequence starting at 1:50, which shows the different responses between monkeys, apes, and humans in the mirror-test.
Medical Research on Animal Models – Where Do You Stand?
Our self-aware cousins
This weekend I heard an incredibly interesting story on NPR's This American Life titled "Almost Human Resources" (Act 3). The story was all about the issues surrounding chimpanzees in the human world surpassing their usefulness and how we should care for them. Apparently this now includes retirement homes with TVs.
This story, along with a recent tangential debate over at Southern Fried Science and PETA's "sea kittens" campaign, sent my mind down a familiar path - one that anyone working in biology inevitably travels from time to time: the ethics of animal research for science.
There have been myriad writings, books, movies, discussions, and laws surrounding the practice of using animals for research. I'm sure most of us in the science world have come to very similar conclusions on the subject, though we may vary widely in the details.
Nonetheless, I'm very interested to hear where YOU, my readers and my fellow scientist peers, currently stand on the subject. I would like this post to be interactive.
First, I'd like to give my own thoughts.
In general, I view all living things as uber-complex organic robots (humans included). All life is amazing, precious, and beautiful - from bacteria to humans - but I still see us all as robots, running our nearly unfathomable genetic programs, developmental processes, and higher-level emergent programs of conscious and sub-conscious thought.
Mirror Test
At the same time, I feel - for no rational reason really - that consciousness and self-awareness inherently grant those that harbor them the right to live relatively free from human induced suffering. This is a feeling. We all feel it, at least for humans. We feel the immorality of conducting experiments on other human beings (though this was not always the case). Why? Because it's...just...wrong.
It's for this reason that I'm completely opposed to any medical research on chimpanzees or any great apes. There is no doubt that our great ape cousins share many if not most of our own emotional and sensory perceptions, as well as similar intellectual abilities (similar in type - not necessarily degree). For all intents and purposes, I see them as people. Not human people. Not anthropomorphized animals. But sentient to semi-sentient beings.
It's hard to measure degrees of self-awareness and know whether another creature has it. But the classic mirror test is one simple way to find when the answer is a clear yes. As of right now, great apes, dolphins, elephants, and at least one bird species, the magpie, have passed the test and shown that they have some understanding of "self."
If a creature can have any understanding of what is being done to "them," I am completely against it. Recently Orac at Respectful Insolence posted on the discontinuation of using dogs for teaching surgery techniques. He caught some flak from a few commenters for showing an emotional relief that dog use was being halted - at least partially because he loves dogs. As if any decisions on the use of other beings for our own benefit could be arrived at using only reason!
No - we as humans place some inherent value on consciousness, on self-awareness. Dogs may or may not be "self-aware" as defined by behavioral scientists. They can't pass the mirror test, but anyone who has had a dog knows that they clearly experience something akin to guilt, and a whole host of emotions similar to those of our own (I'm being careful here not to anthropomorphize). They know when they have done something wrong.
As any behavioral biologist, psychologist, or cognitive neuroscientist knows, there is no clear dividing line between conscious being and automaton. What about rhesus monkeys and the other more "primitive" primates? I personally feel that much monkey research - particularly those studies on the cutting edge of such diseases as A.I.D.S. - are critical right now. However, I also know that I could never be one to perform such studies. There is a mental hypocrisy here in my own mind. I would feel wrong performing primate research. But I support it to a limited extent.
But for some animals, it seems clear when they are well beyond that gray fuzzy line. Xenopus frogs, as far as any observation or measurement can tell, are much too dumb to have any sort of self-awareness. The same can be said of mice or rats. They simply do not have the cognitive capacity - the hardware - to generate emergent properties like self-awareness as we know it. It seems more than clear to science, I believe, that these creatures are fuzzy automatons. I have performed studies (using incredibly regulated and humane methods) using these creatures, and I have no qualms about it, so long as the use of animal models are absolutely critical to the study at hand. Hundreds of thousands of lives have been saved or vastly improved by such studies. Few people alive today (in America at least) can imagine what the state of human health would be without mice and rat studies.
And just to go one level further "down" the evolutionary ladder, consider fish.
Fish are NOT "sea kittens." We understand at least at a basic level what overall types of brain structures and neural pathways are required for higher cognition. Fish do not have these structures. They are insanely complex, from a genetic standpoint. They are beautiful. They are unimaginably important to the ecosystems of the earth. But they are still slimy scaly robotic automatons incapable of "suffering" in any human sense.
And invertebrates? Well, they're clearly organic machines. Would any of you really argue otherwise?
However, with all of the above being said, I often think about how barbaric people were only a generation ago (or sometimes less), and I wonder which of my beliefs will be considered equally barbaric by the next generation. As Richard Dawkins mused in "The God Delusion," perhaps animal rights is the issue upon which our generation will be judged to have sinned. Perhaps our ancestors will cringe at our actions (while praising the 500 year lifespans our research has given them - kidding).
What do you think? Take these polls and leave your comments below.
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